1. Field of the Invention
This invention relates to a pressure gradient control system. More particularly, the invention relates to a pressure gradient control system for use in ventilating a spraying booth divided into a plurality of intercommunicating spraying zones or clean room facilities having a plurality of intercommunicating cleaning zone. This control system is operable to adjust pressure gradients between adjacent zones. The system has a ventilated area divided into a plurality of intercommunicating zones, a zone-to-zone pressure gradient detecting device for detecting pressure gradients between adjacent zones, and a control unit for adjusting quantities of air supply or exhaust to/from the zones based on detection information received from the zone-to-zone pressure gradient detecting device to establish a predetermined pressure gradient between the adjacent zones.
2. Description of the Related Art
The above pressure gradient control system is operable automatically to adjust the pressure gradients between adjacent zones to a predetermined gradient by means of the control unit, thereby to regulate direction and volume of gas flows between the adjacent zones or to eliminate gas flows therebetween. Such automatic control dispenses with manual control of air supply or exhaust to/from the zones. However, no consideration has heretofore been made regarding pressure gradients between the ventilated area and ambient area (see Japanese Utility Model Application No. 1989-87018, for example).
The conventional system carries out adjustment of only relative quantities of air supply or exhaust among the zones, in which the quantities of air supply or exhaust to/from the respective zones are adjusted to a predetermined gradient based on detection of the pressure gradients between adjacent zones. This adjustment does not determine a total quantity of air supply to the ventilated area (i.e. a sum total of quantities of air supplied to the zones) or a total quantity of exhaust therefrom (i.e. a sum total of quantities of exhaust from the zones). In other words, although the predetermined pressure gradient is secured between adjacent zones in the ventilated area, the pressure gradients between the ventilated area and ambient area remain indefinite. Consequently, the conventional system has the disadvantages of undesirable gas flows occurring between the ambient and those of the zones communicating with the ambient, and of producing gas flows counter to a desired direction of gas flows.